Using Collections.binarySearch on a Linked list

Question

hi all
i want to use the Collections.binarySearch method on a linked list object to add items to it. These items are of type Entry (a class i have created).
i have the following code:
public void addEntry(Entry newEntry)
        int pos = Collections.binarySearch(entryList, newEntry);
        if (pos < 0)
            entryList.add(-(pos) -1, newEntry);
[\CODE]
where entryList is declared as:
private List entryList = new LinkedList();
This code compiles OK, but when i run it to add an Entry element to the linked list, i get a ClassCastException being thrown, and im not sure why.
i can add one Entry object to the list ok, but it falls over when i try to add another. im trying to order my Entry objects by a field called 'surname', so the binarySearch finds the correct location in the list for the new entry and then it is added.
any help on this would be appreciated
cheers
david                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       

Answer 1

binarySearch doesn't work on a linked listSo untrue:Well, only mostly untrue. It still doesn't really do a binary search on your linked list
From the javadoc
'This method runs in log(n) time for a "random access" list (which provides near-constant-time positional access). If the specified list does not implement the RandomAccess and is large, this method will do an iterator-based binary search that performs O(n) link traversals and O(log n) element comparisons. '
import java.util.*;
public class Test {
public static void main(String[] args) {
List entryList = new LinkedList();
entryList.add(new Integer(3));
entryList.add(new Integer(5));
entryList.add(new Integer(1));
Collections.sort(entryList);
System.out.println(Collections.binarySearch(entryList,
new Integer(5)));
}Compiles and runs without any problems